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Observation of transition between multimode Q-switching and spatiotemporal mode locking

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Photonics Research 2021年第4期9卷 530-534页

作者： Kewei Liu xiaosheng xiao Changxi Yang State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua UniversityBeijing 100084China State Key Laboratory of Information Photonics and Optical Communications School of Electronic EngineeringBeijing University of Posts and TelecommunicationsBeijing 100876China

We report experimental observation of multimode Q-switching and spatiotemporal mode locking in a multimode fiber laser.A typical steady Q-switching state is achieved with a 1.88μs pulse duration,a 70.14 kHz repetition rate,and a 215.8 mW output power,corresponding to the single pulse energy of 3.08μ*** find weak spatial filtering is essential to obtain stable Q-switched pulses,in contrast to the relatively stronger spatial filtering for spatiotemporal mode ***,a reversible transition process,as well as a critical bistable state,between multimode Q-switching and spatiotemporal mode locking,is achieved with specific spatial coupling and waveplates *** believe the results will not only contribute to understanding the complicated nonlinear dynamics in multimode,fiber-based platforms,but also benefit the development of promising high-pulse energy lasers.

关键词： multimode fiber switched

Real-time collision dynamics of vector solitons in a fiber laser

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Photonics Research 2021年第3期9卷 289-298页

作者： Kangjun Zhao Chenxin Gao xiaosheng xiao Changxi Yang State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua UniversityBeijing 100084China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876China

Particle-like structures of solitons, as a result of the balance between dispersion and nonlinearity, enable remarkable elastic and inelastic soliton collisions in many fields. Despite the experimental observation of temporal vector-soliton collisions in birefringent fibers, collision dynamics of vector solitons in fiber lasers have not been revealed before, to the best of our knowledge. Here, the real-time spectral evolutions of vector solitons during collisions in a dual-comb fiber laser, which generates vector solitons with slightly different repetition rates, are captured by a time-stretch dispersive Fourier transform technique. We record the whole process of vector-soliton collisions, including the formation of weak pulses induced by cross-polarization coupling, opposite central wavelength shifts of both vector solitons, distinct intensity redistribution and dissipative energy, and gradual recovery to initial states. Furthermore, extreme collisions with strong four-wave mixing sidebands are observed by virtue of coherent coupling between the orthogonal polarization components of vector solitons. Numerical simulations match well with the experimental observations. The experimental and numerical evidences of vector-soliton collision dynamics could give insight into the understanding of nonlinear dynamics in fiber lasers and other physical systems, as well as the improvement of laser performance for application in dual-comb spectroscopy.

关键词： fiber polarization solitons

Sub-terahertz-repetition-rate frequency comb generated by filter-induced instabilities in passive driven fiber resonators

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Photonics Research 2022年第2期10卷 465-474页

作者： Pan Wang Jiangyong He xiaosheng xiao Zhi Wang Yange Liu Institute of Modern Optics Nankai UniversityTianjin Key Laboratory of Micro-scale Optical Information Science and TechnologyTianjin 300350China School of Electronic Engineering State Key Laboratory of Information Photonics and Optical CommunicationsBeijing University of Posts and TelecommunicationsBeijing 100876China

Ultrahigh-repetition-rate frequency comb generation exhibits great potential in applications of optical waveform synthesis, direct comb spectroscopy, and high capacity telecommunications. Here we present the theoretical investigations of a filter-induced instability mechanism in passive driven fiber resonators with a wide range of cavity dispersion regimes. In this novel concept of modulation instability, coherent frequency combs are demonstrated numerically with rates up to sub-terahertz level. Floquet stability analysis based on the Ikeda map is utilized to understand the physical origin of the filter-induced instability. Comparison with the well-known Benjamin–Feir instability and parametric instability is performed, revealing the intrinsic distinction in the family of modulation instabilities. Our investigations might benefit the development of ultrahigh-repetition-rate frequency comb generation, providing an alternative method for the microresonators.

关键词： passive fiber repetition

Pattern formation in 2-μm Tm Mamyshev oscillators associated with the dissipative Faraday instability

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Photonics Research 2019年第11期7卷 1287-1295页

作者： Pan Wang Shunyu Yao Philippe Grelu xiaosheng xiao Changxi Yang State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua UniversityBeijing 100084China Laboratoire ICB UMR 6303 CNRS Universite Bourgogne Franche-ComteF-21078 Dijon CedexFrance

We investigate numerically the pattern formation in 2-μm thulium-doped Mamyshev fiber oscillators, associated with the dissipative Faraday instability. The dispersion-managed fiber ring oscillator is designed with commercial fibers, allowing the dynamics for a wide range of average dispersion regimes to be studied, from normal to nearzero cavity dispersion where the Benjamin–Feir instability remains inhibited. For the first time in the 2-μm spectral window, the formation of highly coherent periodic patterns is demonstrated numerically with rates up to ~100 GHz. In addition, irregular patterns are also investigated, revealing the generation of rogue waves via nonlinear collision processes. Our investigations have potential applications for the generation of multigigahertz frequency combs. They also shed new light on the dissipative Faraday instability mechanisms in the area of nonlinear optical cavity dynamics.

关键词： dynamics. Faraday dissipative

Buildup dynamics of multiple solitons in spatiotemporal mode-locked fiber lasers

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Photonics Research 2021年第10期9卷 1898-1906页

作者： KEWEI LIU xiaosheng xiao YIHANG DING HONGYAN PENG DONGDONG LV CHANGXI YANG State Key Laboratory of Precision Measurement Technology and Instruments Department of Precision InstrumentsTsinghua UniversityBeijing 100084China State Key Laboratory of Information Photonics and Optical Communications School of Electronic EngineeringBeijing University of Posts and TelecommunicationsBeijing 100876China School of Physics and Electronic Engineering Hainan Normal UniversityHaikou 571158China

Spatiotemporal mode locking is a nonlinear process of multimode soliton *** the real-time buildup dynamics of the multiple solitons in a spatiotemporal mode-locked multimode fiber laser are investigated,assisted by the time-stretch *** find that the buildup processes are transverse mode dependent,especially during the stages of relaxation oscillation and Q-switching prior to multiple soliton ***,we observe that the transverse modal composition of these generated pulses among the multiple solitons can be different from each other,indicating the spatiotemporal structure of the multiple soliton.A simplified theoretical model based on pulse energy evolution is put forward to interpret the role of 3D saturable absorber on spatiotemporal structures of spatiotemporal mode-locking multiple *** work has presented the spatiotemporal nonlinear dynamics in multimode fiber lasers,which are novel to those inside the single transverse mode fiber lasers.

关键词： fiber mode solitons

波长可调节全正色散掺镱锁模光纤激光器的放大特性(英文)

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红外与激光工程 2014年第12期43卷 3924-3927页

作者：华弋肖晓晟清华大学精密仪器系精密仪器与测量技术国家重点实验室北京100084

高功率,波长可调超短脉冲光源具有重大的应用价值。采用掺镱光纤放大的全正色散锁模光纤激光器能够满足以上优质光源的要求,并且结构紧凑。通过实验全面探索了波长可调节全正色散锁模光纤激光器的放大特性。分析了小信号增益系数随着信... 详细信息

高功率,波长可调超短脉冲光源具有重大的应用价值。采用掺镱光纤放大的全正色散锁模光纤激光器能够满足以上优质光源的要求,并且结构紧凑。通过实验全面探索了波长可调节全正色散锁模光纤激光器的放大特性。分析了小信号增益系数随着信号光波长的变化。发现最大增益出现在波长为1 030 nm附近,并且增益随着信号光波长的增大而减小,这是由于掺镱光纤的增益谱特性决定的。也分析了增益系数随泵浦光功率的变化,观察增益饱和现象和放大自发辐射噪声。也讨论了种子脉冲在放大器中的时域与频域畸变。发现脉冲因为群速度色散而轻微展宽,频谱因为自相位调制也会发生轻微展宽。

关键词：放大器全正色散锁模

Electrical Measurement to Assess Hydration Process and the Porosity Formation

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Journal of Wuhan University of Technology(Materials Science) 2008年第5期23卷 761-766页

作者：魏小胜 Department of Civil Engineering Huazhong University of Science and Technology

The change of electrical resistivity with time at early ages was used to investigate the hydration process and the porosity development. Porosity reduction process of cement-based materials hydration was developed by a proposed method. The porosity reduction is fast at the setting period. The results find that the pore discontinuity occurs faster at lower water/cement ratios than at higher water/cement ratios which is similar to the results of the Percolation method.

关键词： electrical resistivity hydration setting time percolation

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高功率超快光纤激光器研究进展

中国激光 2019年第5期46卷 77-88页

作者：余霞罗佳琪肖晓晟王攀新加坡国立大学电子与计算机工程系新加坡119077 南洋理工大学电子电气工程系新加坡639798 清华大学精密仪器系精密测试技术与仪器国家重点实验室北京100084

高功率超快脉冲激光应用广泛,包括精密工业加工、超快光谱学、强场物理学及军事应用等。光纤激光具有操作方便、散热要求低、光束质量好等优势。综述了近年来高功率超快光纤激光器的研究进展,包括新兴的被动锁模光纤激光技术及啁啾脉冲... 详细信息

高功率超快脉冲激光应用广泛,包括精密工业加工、超快光谱学、强场物理学及军事应用等。光纤激光具有操作方便、散热要求低、光束质量好等优势。综述了近年来高功率超快光纤激光器的研究进展,包括新兴的被动锁模光纤激光技术及啁啾脉冲放大技术,以高功率超快光纤激光器在高次谐波产生中的应用为例,阐述了高能量光纤激光在非线性光学中的优势,对高功率超快光纤激光器的研究前景进行了展望。

关键词：非线性光学光纤激光器锁模激光器啁啾脉冲放大高次谐波

All-fiber spatiotemporal mode-locking lasers with large modal dispersion

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Photonics Research 2022年第2期10卷 483-490页

作者： Huaiwei Zhang Yunhong Zhang Jiying Peng Xinyang Su xiaosheng Xia Dongjian Xu Junhao Chen Tianran Sun Kai Zheng Jianquan Yao Yi Zheng Key Laboratory of Luminescence and Optical Information Ministry of EducationBeijing Jiaotong UniversityBeijing 100044China State Key Laboratory of Information Photonics and Optical Communications School of Electronic EngineeringBeijing University of Posts and TelecommunicationsBeijing 100876China

It is a challenging problem to balance the modal walk-off(modal dispersion) between multiple transverse modes and chromatic dispersion in long step-index multimode fibers(MMFs). By properly designing the oscillator, we have overcome the difficulty and successfully obtained an all-fiber spatiotemporal mode-locked laser based on step-index MMFs with large modal dispersion for the first time, to our knowledge. Various proofs of spatiotemporal mode-locking(STML) such as spatial, spectral, and temporal properties, are measured and *** laser works at a fundamental frequency of 28.7 MHz, and achieves a pulse laser with single pulse energy of 8 nJ, pulse width of 20.1 ps, and signal-to-noise ratio of-70 dB. In addition, we observe a dynamic evolution of the transverse mode energy during the STML establishment process that has never been reported before.

关键词： fiber dispersion modal